Modeling of PANDA isolation condenser experiments with MELCOR and Apros

Abstract Modeling methods were developed for passive cooling systems, in which steam condenses in vertical tubes. Isolation condenser experiments performed in the PANDA facility were calculated with two computer codes: the severe accident code MELCOR, and the process simulation software Apros. Both pure steam tests and tests with steam–non-condensable gas mixtures were calculated. Recommendations are given for MELCOR users regarding an appropriate nodalization, flow path definition, and heat transfer parameters. With proper model parameters and nodalization, both MELCOR and Apros codes are able to calculate the operation of the passive cooling system well.